Method of preventing end checking in the artificial seasoning of wood



Dec. 30, 1952 M. s. HUDSON 2,623,300

METHOD OF PREVENTING END CHECKING IN THE ARTIFICIAL SEASONING 0F WOOD Filed June 15, 1950 Fi i IN V EN TOR.

MON/E '5'. H1108 0 7M 769124449 1 Sm A TTORNEYJ Patented Dec. 30, 1952 METHOD OF PREVENTING END CHECKING IN THE ARTIFICIAL SEASONING OF WOOD Monie S. Hudson, Spartanburg, S. 0.

Application June 13, 1950, Serial No. 167,890

Claims.

This invention relates to processes for season ing wood by artificial means, and more particularly to the prevention of end checking during such processes.

A process of this sort in which organic vapors are employed as the drying medium is described in my prior Patents Nos. 2,273,039, 2,435,218, and 2,435,219, and by which wood may be seasoned or dried effectively in a considerably shorter period than has been possible by artificial drying processes previously in use. The rapid rate at which wood may be dried according to the process described in the above noted patents, however, raises difiiculties in some instances because of the tendency of wood to end check. The same diificulty with end checking is encountered in other artificial seasoning processes, such as kiln drying, Boultonizing in which the wood is boiled in oil under vacuum, and steaming.

This end checking results from the fact that wood shrinks as it dries, which shrinkage sets up stresses in the wood, and as the moisture from the central section of the wood must travel outward through the end portions, the end portions are kept moist because of the passage of water vapor through them and therefore have insufficient strength to withstand the stresses focused on them by drying of the central section, so that the end portions may be split or checked as a result of these stresses.

According to the present invention, this difficulty is obviated by boring transverse holes through the end portions of the wood before subjecting it to artificial drying. Such holes act as vents allowing moisture released from the central section of the wood to come off without passing through the end portions, so that the end portions may be dried rapidly during the early stages of the drying process and thereby obtain strength sufiiciently high to resist end checking due to the shrinkage stresses set up as the drying process is carried out. Comparable end boring of wood to be air seasoned has been tried in developing the present invention, but has not been found effective, apparently because the end portions of the wood are maintained during air seasoning in equilibrium at about the fiber saturation point and never dry down enough to get the early dry strength obtainable in an artificial seasoning process.

The invention may be illustrated with reference to its application in the artificial drying of crossties by the process described in my above noted prior patents. By this process, the crossties are dried by placing them in a closed space and maintaining a drying atmosphere of highly heated organic vapors in this closed space until the desired degree of dryness is obtained. The manner in which the crossties are end bored in accordance with the present invention before placing them in the closed space for drying is illustrated in the accompanying drawing, in which:

Fig. 1 is a fragmentary perspective view of an end bored crosstie;

Fig. 2 is a sectional detail taken substantially on the line 12-2 in Fig. 1;

Fig. 3 is a further perspective view corresponding generally to Fig. l; and

Fig. 4 is a sectional detail taken substantially on the line i4 in Fig. 3.

Crossties, such as are shown fragmentarily at Ill in the drawings, are conventionally about 8 /2 feet in length and have cross-sectional dimensions of 6 by 6 to 7 by 9 inches. About 12 to 20 inches from each end a tie plate dap I2 is adzed into the top face of the crosstie, and suitably spaced holes I4 are bored at the dap I2 for receiving the tie plate spikes, usually by passing the crosstie through an adzing and boring machine arranged to work it for the tie plates in this manner.

The transverse holes bored at the ends of the crosstie according to the present invention may be conveniently placed in the crosstie as it is passed through this adzin and boring machine. These holes should in general be spaced at least 1 inch from the ends of the crosstie so that the end portions beyond the holes will be of sufiicient size to develop adequate early strength as a result of their rapid drying to resist the stresses tending to induce end checking, and should be arranged in a pattern such that at least 20% of the projected cross-sectional area of the crosstie is removed, but may otherwise be located between the tie plate dap l2 and the end of the crosstie in any desired arrangement, and they may be bored either from the top face through to the bottom face as at it in Fig. 1, or through the side faces as at #3 in Fig. 3. These transverse holes it: or iii in no way adversely affect the value of the crossties in service.

Fig. 1 of the drawings illustrates a pattern of end boring that has beenfound to give satisfactory results in a 7 by 9 inch crosstie, and in which the transverse borings I 6 extending from the top 9 inch face through the bottom face are /2 inch in diameter and are staggered on centers 2 inches apart. This arrangement results in removing about of the projected cross-sectional area, while removing less than 0.2% by volume of the wood in the crosstie. Fig. 3 illustrates an alternative arrangement of end borings l8 through the side faces of the crosstie It. As already noted, the transverse holes IE or it may also be arranged in any other convenient or desired pattern, although it is recommended that holes not smaller than ,4 inch or larger than 1 inch in diameter be used.

The effectiveness of an arrangement of transverse end borings in accordance with the present invention in preventing end checking is attributable to the fact that they isolate the end portions of the wood so that theseend portions attain their dry strength early in the drying process. The relation of rapid drying of the end portions to the development of strength sufficient to withstand end checking is indicated by the fact that drying wood from 90 to 30 per cent moisture content by weight does not appreciably increase the strength of the wood, but upon drying from-.30 to '20 per cent the strength is increased about one-third, and further increases in strengthof about one-third are obtained upon drying to 10 per cent, and from 10 to 0 per cent.

The present invention, as described above and defined in the appended claims, is applicable generally for use in preventing end checking in processes of artificial seasoning of wood.

I claim:

1. The'process of artificially seasoning elongated wood stock in which the grain runs longitudinally, which comprises boring holes in a transverse zon adjacent'the end faces of said wood stock, and then subjecting said Wood stock to artificial seasoning, whereby the end portions of said wood stock are conditioned for drying rapidlyand thereby attaining an early dry strength sufficiently high to resist end checking during said seasoning.

2.. The process'of artificially seasoning elongated wood stock in which thegrain runs longitudinally, which comprises boring holes through said wood stock in a transverse zone adjacent the endfaces thereof, said holes being arranged in'a pattern such that at least 20% of the projected transverse cross-sectional area of said wood stock is removed, and then subjecting said wood vstock to artificial seasoning, whereby the end portions of said wood stock are conditioned for. dryingj rapidly and thereby attaining an checking duringsaid seasoning.

.earlydrystrength sufficient :high to resist end 3. In th process of artificially seasoning elongated wood stock having the grain running 1ongitudinally thereof by drying said wood stock in a closed space with organic vapors, the improvement which comprises boring holes through said wood stock in a transverse zone adjacent the end faces thereof and in a pattern such that at least 20% of the projected transverse crosssectional area of said wood stock is removed, and then subjecting said wood stock to said drying treatment with organic vapors, whereby the end portions of said wood stock are conditioned for drying rapidly and thereby attaining an early dry strength sufficiently high to resist end checking during said drying treatment.

4. The process of seasoning crossties by artificial means, which comprises boring holes through said crossties adjacent the end faces thereof in a transverse zone between the tie plate daps and said end faces and in a pattern such that at least 20% of the projected transverse cross-sectional area of said crossties is .removed, and then subjecting said crosties to artificial seasoning, whereby the end portions of said crossties are conditioned for drying rapidly and thereby attaining an early dry strength sufficiently high to resist end checking during said seasoning.

5. In the process of drying crossties in a closed space with organic vapors, the improvement which comprises boring holes through said crossties in a transverse zone between the tie plate daps and the end faces of said crossties and in a pattern such that at least 20% of the projected transverse cross-sectional area of said crossties is removed adjacent eachend face-and then subjecting said crossties to artificial seasoning, whereby the end portions of saidcrossties are conditioned for drying rapidly and thereby attaining an early dry strength sufficiently high to resist end checking during said drying process.

MONIE S. HUDSON.

REFERENCES CITED The following references .are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 987,392 Mitchell Mar. 21, 1911 1,936,439 Siever Nov. 21, 1933 2,470,514 Muller May 17, 1949 

